Another direction to go for depth of sound stage specifically: audiokenesis sound generator horns... rear-firing add-on speakers: they work (in my system).For sure they are based on the "timing" between late and early reflection and particularly back reflection...
But it is possible to use the right material passive treatment and the right active controls with Helmholtz resonators at no cost to generate this space....Without speaker addition....But it is less esthetical...
I prefer solution at no cost anyway... 😊